This final case-study will focus on aniseikonia
, which is another problem that can be associated with anisometropia.
However, patients with aniseikonia
have been shown to still pass RDS testing, demonstrated in patients with monocular aphakia with a large amount of aniseikonia
Significant astigmatism can also produce axial aniseikonia
, as in the prescription below:
The refractive combination has resulted in gross anisometropia and, therefore, aniseikonia
needs to be considered when dispensing this patient.
Spectacle wearers with a large degree of anisometropia and good visual acuities may experience aniseikonia
. The symptoms include visual discomfort, visual distortion of space and sometimes difficulty in achieving good binocular vision resulting from a difference in image size.
Professor Evans also promoted the benefits of contact lenses for correcting anisometropia by reducing differential prismatic effects and mitigating aniseikonia
. Most importantly, by providing a more potent binocular stimulus to the visual system, correcting anisometropia with contact lenses creates the opportunity to improve lifelong visual outcomes for these patients.
(10-13) Specifically, the research indicates that for both refractive and axial anisometropia, contact lenses minimise aniseikonia
and, therefore, maximise the potential for normal binocular vision.
01 The spectacles shown in the image are designed to help compensate for aniseikonia
. In the case illustrated would you expect that:
A potential problem could be that the image size in one eye is so different in size to the other eye (aniseikonia
) that binocular fusion is not possible, eg in unilateral aphakia.
will be reduced with contact lenses compared with spectacles
a) There will be reduced effects of aniseikonia
A seminal paper in 1988 showed that for all types of anisometropia, contact lenses are better than spectacles at controlling aniseikonia
. (10) These authors noted that in children with anisometropia, contact lenses provide a more potent stimulus to the binocular system.